The present invention relates to organomolybdenum compositions having high molybdenum content, which are useful as lubricant additives. The organomolybdenum compositions of the present invention are the reaction products of a fatty oil reacted with a diamine, followed by further reaction of the resulting intermediate with a molybdenum source to form the organomolybdenum product compositions, in which the process does not require a volatile organic solvent to promote and achieve high molybdenum incorporation in the additive product, nor does it require sulfur-containing or phosphorus-containing reactants nor post-reaction filtration removal for unreacted molybdenum source reactant.
Lubricating oils used in the internal combustion engines of automobiles or trucks are subjected to a demanding environment during use. Among other adverse effects, this environment can lead to oxidative degradation of the oil. This oxidation of the oil is catalyzed by the presence of certain impurities in the oil, such as iron compounds. This oxidation also is promoted by the elevated temperatures to which the oil is subjected during use. The oxidation of lubrication oils during use is usually controlled in part by the use of antioxidant additives, which may extend the useful life of the oil, particularly by reducing or inhibiting unacceptable increases in the viscosity of the oil.
Various molybdenum compounds have been used and proposed as performance-enhancing additives for lubricant compositions. For instance, there are numerous examples in the patent literature which describe the use of molybdenum additives variously as antioxidants, deposit control additives, anti-wear additives and friction modifiers, in lubricant compositions. A partial list of such patent references includes, for example, U.S. Pat. Nos. 4,164,473, 5,840,672, 6,103,674, 6,174,842, and U.S. Reissued Pat. No. RE37,363 E, among others.
The preparation of organomolybdenum additives generally requires complicated reaction steps that add considerable cost to the manufacturing of these additives. Examples of some costly processing steps in this respect are as follows:
1. The use of volatile organic compound (xe2x80x9cVOCxe2x80x9d) solvents, such as toluene, xylenes, 2-propanol, and dimethylformamide add considerable cost to the production of organomolybdenum compounds.
2. Low levels of molybdenum incorporation into the lubricant additive itself are achieved, which increases cost because higher concentrations of the resulting organomolybdenum product/additive must be used in the oil to deliver the required level of molybdenum to the crankcase package or finished oil. Ideally, it would be desirable to produce these organomolybdenum products/additives having molybdenum contents above 8 percent by weight, and preferably above 10 percent by weight.
3. Filtration is generally required to remove unreacted inorganic molybdenum. Unreacted molybdenum adds considerable cost to the production of organomolybdenum compounds because inorganic molybdenum is an expensive raw material.
4. Other costly processing steps associated with prior schemes for producing organomolybdenum components or lubricant additives include the need for acid or base neutralizations, the use of expensive catalysts or promoters, and water washes.
Examples of such prior processes for making organomolybdenum components or lubricant additives are reported, for example, in the patent literature as follows:
EP 1 136 496 discloses a product derived from methylaminopropylamine (R contains 1 carbon), which shows limited solubility in oil, while products containing 6 or more carbons in the R group have low molybdenum content (less than or equal to 8% undiluted).
EP 1 136 497 discloses molybdenum compounds derived from carboxylic acids and glycerides, which are relatively expensive.
U.S. Pat. No. 4,889,647 discloses molybdenum products that have relatively low molybdenum contents, for example 6 percent by weight, or lower.
U.S. Pat. No. 6,103,674 discloses molybdenum products that have low molybdenum contents, for example, 8 percent by weight or lower, and which contain sulfur.
Sulfur can be an undesirable component in engine oils. At high temperatures and under severe conditions, even the less aggressive forms of sulfur can cause corrosion, and in some cases elastomeric seal incompatibility (e.g., rubber hardening). Ideally, therefore, molybdenum compounds intended for use in lubricant engine oils should have minimal sulfur content.
U.S. Pat. No. 4,692,256 discloses a process for making an organomolybdenum compound that requires neutralization steps and water separations in order to isolate the organomolybdenum compound. When water is used as a promoter, as in U.S. Pat. No. 4,692,256, a filtration is required to remove unreacted molybdenum.
U.S. Pat. No. 5,137,647 discloses a sulfur and phosphorous-free organomolybdenum complex of organic amide, such as molybdenum containing compounds prepared from the reaction of fatty derivatives of 2-(2-aminoethyl)aminoethanol with a molybdenum source, in which the reaction temperature can be as high as 160xc2x0 C. The sole example provided therein has a reaction temperature ranging from 130xc2x0 C. to 140xc2x0 C., and a filtration is carried out. Also, the reaction product is filtered, which adds an additional processing step.
U.S. Pat. No. 4,765,918 discloses molybdenum-containing compositions derived from fatty oils, amines, and a sulfur source.
U.S. Pat. No. 5,412,130 discloses molybdenum products derived from specially pre-treated fatty oils, e.g., treated by epoxidation followed by alkylation, that are reacted with molybdenum using a very specific fatty oil-derived catalyst. This special pre-treatment of the fatty oil adds considerable cost to the resulting product, making it impractical for use in lubricants.
The above problems suggest a previously unfulfilled need in the lubricant additive and composition industry and related technologies for oil soluble, sulfur-free molybdenum additives having high molybdenum content and low tendency to discolor finished oils without the need to use volatile solvents and without the need to remove non-reacted molybdenum. It has unexpectedly been found that the molybdenum additives of the present invention provide the above benefits to lubricating compositions without the attendant problems.
The present invention is directed to unique organomolybdenum compositions, which are especially useful as lubricant additives. To form the organomolybdenum compositions of this invention, a fatty oil, a diamine and a molybdenum source are combined in the absence of a volatile organic solvent yet effective to form a high organo molybdenum content reaction product. This reaction product obtained also does not have to be filtered to remove unreacted molybdenum source material.
In a more particular aspect, the present invention is directed to an organomolybdenum composition comprising the reaction product of a fatty oil reacted with an aliphatic diamine, followed by further reaction of the resulting intermediate reaction product with a molybdenum source in the absence of volatile organic solvent and without need for post-reaction filtering. In one preferred aspect, the first process step is performed neat, while in the second process step a small amount of water, but no volatile organic solvent is introduced or present during the molybdenum incorporation reaction, sufficient for the molybdenum source ingredient to go into solution such that reaction still proceeds well.
In one further aspect, the diamine reactant used is a monsubstituted amine having high hydrocarbon character, such as represented by the following general structure: 
where x is 1 or 2, and R is a hydrocarbon-containing group containing at least about 6 carbon atoms. In one preferred aspect, the R group also contains oxygen, such as where R represents an alkyloxyalkylene group.
In another aspect, this invention provides a low cost process for producing sulfur- and phosphorus-free organomolybdenum compositions with high molybdenum content. In one aspect, the high molybdenum content of the reaction products of the process of the invention comprises from about 8 wt % to about 15 wt % molybdenum content (Mo). In addition, the process improvements achieved do not require the use and presence of a volatile organic solvent to achieve highly effective incorporation of molybdenum in the reaction product, and the resulting reaction product also does not require filtration to remove unreacted molybdenum source material such as molybdenum trioxide. The molybdenum-containing lubricant additives of the present invention are also very effective as antioxidants and deposit control additives in crankcase oils. Also, it has unexpectedly been found that preparation of the organomolybdenum compositions at reduced reaction temperatures according to another aspect of the present invention results in an improvement in the deposit control performance of the reaction product when used as an additive in engine oils. The molybdenum-containing lubricant additives of the present invention also are light colored complexes that are not prone to discoloration even when used at high concentrations in crankcase oils.
In an embodiment of the present invention, the reaction scheme used to prepare the molybdenum additives includes a two step process. The first included step involves preparing an organic ligand comprised of an aminoamide/glycerol carboxylate mixture. This mixture is prepared by combining, mixing, contacting, or reacting (a) a fatty oil, vegetable oil, triglyceride or other glycerol ester of a higher fatty acid with (b) a mono-substituted alkylene diamine at an elevated temperature with heating. The second step involves carrying out the molybdenum incorporation.
Fatty Oils
Examples of preferred fatty or vegetable oils that may be used in the process of the present invention include groundnut oil, coconut oil, linseed oil, palm kernel oil, olive oil, cottonseed oil, grapeseed oil, corn oil, canola oil, palm oil, peanut oil, safflower seed oil, sesame seed oil, caster oil, rapeseed oil (low or high erucic acids), soyabean oil, sunflower oil, herring oil, sardine oil, lard, menhaden oil, hazel nut oil, walnut oil, and tallow, and mixtures thereof. These fatty or vegetable oils can include those compounds generally known as triglycerides, which have the general structure as shown below: 
where R, Rxe2x80x2 and Rxe2x80x3 independently represent saturated or unsaturated aliphatic hydrocarbon groups having from about 8 to about 22 carbon atoms, and preferably are hydrocarbon chains having about 12 to about 22 carbon atoms. Mono- and diglycerides, either separately or in mixtures with one or more triglycerides, are also useful as fatty or vegetable oils in the present invention, in which the R, Rxe2x80x2, or Rxe2x80x3 groups present have the same above meaning.
The Diamine
In order to improve solubility of the organomolybdenum product in base oils and finished oils, it is important for the mono-substituted diamine to have a high hydrocarbon character. For example, the diamine can be represented by the following general structure: 
where x is 1 or 2, and R is a hydrocarbon-containing group containing a minimum of about 6 carbon atoms. R can be aliphatic or aromatic. R, in addition to the minimum of about 6 carbon atoms, may also contain oxygen, but preferably R does not include sulfur or additional nitrogen. It is preferred that R contains a minimum of 10 carbon atoms in order to further improve the organomolybdenum product solubility in base oil. The most preferred R contains an oxygen in addition to the carbons, such as where R is an alkyloxyalkylene group. Where R represents an alkyloxyalkylene group, R can be represented by the structure xe2x80x94X1xe2x80x94Oxe2x80x94X2, where X1 is an alkylene of 2, 3 or 4 carbons and preferably is propylene or ethylene, and X2 is an alkyl moiety having 3 to 30 carbon atoms, more preferably an alkyl moiety having 7 to 20 carbon atoms, and where X2 can be a straight or branched, saturated or partially unsaturated hydrocarbon chain. In diamines in which R is represented by such an alkyloxyalkylene group, both high incorporation of molybdenum, e.g., greater that 8.0 wt. % molybdenum incorporation, in to complexed product, as well as adequate oil-solubility are well imparted to the reaction product. The use of a diamine including an R group represented by xe2x80x94X1xe2x80x94Oxe2x80x94X2 as defined herein in the reaction process makes it possible to maximize the level of molybdenum incorporation levels in the oil soluble reaction product while performing the process without the use of volatile organic processing solvents.
Examples of some mono-substituted diamines that may be used include phenylaminopropylamine, hexylaminopropylamine, benzylaminopropylamine, octylaminopropylamine, octylaminoethylamine, dodecylaminopropylamine, dodecylaminoethylamine, hexadecylaminopropylamine, hexadecylaminoethylamine, octadecylaminopropylamine, octadecylaminoethylamine, isopropyloxypropyl-1,3-diaminopropane, octyloxypropyl-1,3-diaminopropane, decyloxypropyl-1,3-diaminopropane, isodecyloxypropyl-1,3-diaminopropane, dodecyloxypropyl-1,3-diaminopropane, tetradecyloxypropyl-1,3-diaminopropane, isodecyloxypropyl-1,3-diaminopropane, isododecyloxypropyl-1,3-diaminopropane, isotridecyloxypropyl-1,3-diaminopropane. Mono-substituted diamines derived from fatty acids may also be used. Examples include N-coco alkyl-1,3-propanediamine (Duomeen C), N-tallow alkyl-1,3-propanediamine (Duomeen T), and N-oleyl-1,3-propanediamine (Duomeen O), all obtained from Akzo Nobel.
In order to produce an additive reaction product with a high molybdenum content, it is preferred to use a molar ratio of diamine to fatty oil in the first process step varying from about 1.50:1 to 3:1. A more preferred ratio is from about 1.75:1.0 to about 2.5:1.0.
The reaction between the fatty oil and mono-substituted diamine is carried out according to one embodiment at a temperature between about 100 and about 150xc2x0 C. by combining the two materials and heating with mixing and under a nitrogen atmosphere. The preferred reaction temperature is between 110 and 130xc2x0 C. Reaction times may vary from 1 hour to 6 hours. A reaction solvent, such as an organic reaction solvent, is not required.
As mentioned supra, the second included step of the process of the present invention involves carrying out the molybdenum incorporation, which is described in more detail below.
Molybdenum Source
A preferred molybdenum source is molybdenum trioxide. The use of molybdenum trioxide results in effective molybdenum incorporation into the organic ligand made by the aforementioned first process step, and it produces a reaction mass by the completion of the second step that does not require filtration if the reaction is performed properly according to guidance provided herein. Any purity grade of molybdenum trioxide may be used but high purity molybdenum trioxide is thought more likely to produce a product that does not require filtration.
Molybdenum Incorporation
A molybdenum source, such as molybdenum trioxide, and water are added to an aminoamide/glycerol carboxylate reaction mass obtained from the first process step and maintained at approximately 80xc2x0 C. The molar ratio of molybdenum trioxide to diamine can vary from about 1:1.25 to about 1.25:1, and is preferably between 1:1.25 and 1:1 in order to maximize molybdenum content and at the same time reduce or eliminate the presence of unreacted molybdenum trioxide, which thus reduces or eliminates the need for filtration. The amount of water used in this second step should be an amount sufficient to incorporate all the molybdenum trioxide into the aminoamide intermediate and is generally equivalent to the amount of molybdenum trioxide used, but lower and higher levels of water may be used. After addition of the molybdenum trioxide and water the reaction components are slowly heated to reflux temperature with gradual removal of water. Water may be removed by vacuum distillation. The reaction may be carried out at temperatures ranging from 100xc2x0 C. to 150xc2x0 C., however, it has been found that temperatures below 140xc2x0 C. are preferred for producing a molybdenum compound that is highly effective as a deposit control additive. The most preferred reaction temperature is below 130xc2x0 C. The reaction generally requires 1 to 10 hours to remove all the water and this time will vary depending on the reaction temperature selected and the level of vacuum applied. During the water removal a diluent may be added to reduce the viscosity of the final product. However, a diluent is not required for the molybdenum incorporation. Preferred diluents include non-volatile diluents such as aromatic, paraffinic, and naphthenic process oils and base oils as well as synthetic oils and polyalphaolefins. A main advantage of this process is that a volatile organic solvent, such as toluene or xylenes, is not required in the second step for the water removal procedure or otherwise, nor are such organic solvents even used in the preferred embodiment.
At the end of the reaction period, the mixture is cooled and may be filtered to remove any unreacted molybdenum trioxide. Moreover, if the reaction is run optimally, filtration is not required, as tangible amounts of unreacted molybdenum trioxide will not be present. That is, the reaction step of molybdenum incorporation goes essentially to 100% completion. It is preferred to produce a reaction mass with complete molybdenum incorporation so that no post-reaction filtration is required to remove any unreacted molybdenum source material such as molybdenum trioxide. The product prepared by this process is a dark, amber wax or viscous liquid.
Further, when the molybdenum incorporation is performed at or below 130xc2x0 C., improved deposit control in engine oils is achieved using the resulting additive product of the process of the invention.
The preferred combination of mono-substituted diamine, triglyceride, fatty oil or vegetable oil, and molybdenum trioxide, is that which produces a molybdenum content, undiluted with oil, greater than 8 wt. %, and preferably between 10 wt. % and 15 wt. %.
It is also an unexpected discovery that carrying out the molybdenum incorporation reactions at reduced temperatures improves the deposit control properties of the molybdenum product produced. This is demonstrated in the examples provided herein. It is therefore preferred to carry out the molybdenum incorporation reactions between 80 and 140xc2x0 C., more preferably between 100 and 125xc2x0 C.
The high molybdenum content organomolybdenum compositions of the present invention are useful to improve deposit control, antioxidant, antiwear, and/or friction modifiying properties of lubricant oils, and like materials. The inclusion of the present molybdenum compounds generally removes the need for supplementary deposit control or antioxidants, antiwear additives and the like. However, a supplementary deposit control, antioxidant, and/or antiwear additive may be included in the finished oils including the molybdenum additives of the present invention that are less oxidatively stable or in oils that are subjected to unusually severe conditions. The treat rates of the molybdenum additives depend upon the desired finished lubricant properties, however, typically the additives are present in an amount so as to provide at least about 50, and preferably from about 50 to about 1000 ppm, of molybdenum to the finished product. The concentration of molybdenum in the lubricants according to the invention has no particular upper limit, however, for economic reasons a maximum level of about 1000 ppm is generally preferred although not required.
As an important aspect of the present invention, a process for making an organomolybdenum additive has been discovered which can be performed in the absence of volatile organic solvent without sacrificing the level of molybdenum incorporation or oil solubility of the reaction product. This process thus avoids the production and handling costs that otherwise would be associated with using such additional chemicals in performing the process. The language xe2x80x9cabsence of volatile organic solventxe2x80x9d means no volatile organic solvent is intentionally introduced or otherwise permitted to be present with the diamine, fatty oil and intermediate reaction product during the process of the present invention in amounts that might exceed trace amounts, that is, the amount of volatile organic solvent present, if any, during the process is less than 3.0 wt. % of the total reactor contents. From this standpoint, the process of the present invention consists essentially of the reaction product of fatty oil, diamine, and molybdenum source.
In addition, the organomolybdenum compositions of the present invention can be prepared without introducing sulfur or phosphorus. The organomolybdenum complex reaction products are substantially sulfur-free in the sense that the reaction itself introduces no sulfur into the reaction product, although some negligible trace levels of sulfur which are not part of the molybdenum product itself might be present due to impurities or catalysts left behind from the manufacturing process. Preferably, the amount of any sulfur in the organomolybdenum reaction product is less than 0.05 wt. %.
Sulfur can cause corrosion and elastomeric nitrile seal compatibility-hardening problems, among other things, while phosphorus can reduce automobile catalyst compatibility such as when used in crankcase oil formulations. The organomolybdenum compositions of the present invention can be formed free or at least substantially free of sulfur and phosphorus because no reactants including such materials are needed, nor used in the preferred embodiments.
When formulated into a lubricating oil, the organomolybdenum additives of the present invention optionally can be used in combination therein with one or more other additives including those typically used in lubrication oils. Typical additives used in lubrication oils, which optionally can be used in this respect, include detergents, corrosion inhibitors, rust inhibitors, additional antioxidants, dispersants, foam inhibitors, additional antiwear agents, additional friction modifiers, demulsifiers, VI improvers, pour point depressants, zinc dialkyldithiophopshates (ZDDP), and so forth. Examples of such optional supplemental additives are described, for example, in U.S. Pat. No. 5,840,672, which teachings are incorporated herein by reference.
The organomolybdenum compositions of the present invention are xe2x80x9coil solublexe2x80x9d in the sense that they are oil-soluble or capable of being solubilized under normal blending or use conditions into a lubrication oil or diluent for the concentrate.
The overall composition of a lubricating oil including the organomolybdenum additive such as described herein can vary significantly based on the customer and specific application. The additive of this invention can be employed in a variety of lubricating oil base stocks, such as derived from natural lubricating oils, synthetic lubricating oils or mixtures thereof. These oils include typical crankcase lubrication oils for spark-ignited and compression-ignited internal combustion engines, for example natural gas engines, automobile and truck engines, marine, and railroad diesel engines.
These oil base stocks can include, for example, hydrocracked base oils; mineral oils such as paraffinic, naphthenic or mixtures thereof; vegetable oils; petroleum oils, oils derived from coal shale; silicon-based oils; halosubstituted hydrocarbon oils; esters of dicarboxylic acids with alcohols; wax isomerate oils; polyalphaolefins, and mixtures thereof. In one preferred non-limiting embodiment, the base oils used in forming the lubricating compositions of the present invention are characterized by the presence of a high level of saturates and a very low level of sulfur, and include base oils referred to in the petroleum additive industry as Group II and Group III base oils. Further details on such base oils are described, for example, in U.S. Pat. No. 5,840,672, which teachings are incorporated herein by reference. In one non-limiting illustration, the base oils generally contain greater than or equal to 90% saturates, less than or equal to 0.03 weight percent sulfur and have a viscosity index of greater than or equal to about 80. The base oil typically has a viscosity generally of about 2 to about 15 cSt at 100xc2x0 C.
In one non-limiting embodiment, the lubricant oil can be a formulated oil comprising between about 75 to about 95 weight percent (wt %) of a base oil of lubricating viscosity, between 0 and 30 wt % of a polymeric viscosity index improver, between about 5 and 15 wt. % of an additional additive package and typically a sufficient amount of molybdenum complex to provide at least about 50 ppm of molybdenum to the finished lubricant. The optional supplemental additives, for example, could be a supplemental detergent/inhibitor additive package and/or viscosity index improver. The present invention also encompasses the improved lubricating oil compositions, which contain the organomolybdenum additives of the present invention.
The organomolybdenum additives of the present invention can be used in lubricating oils such as crankcase oils for internal combustion engines, as well as gear lubricants, hydraulic fluids, automatic transmission fluids, turbine lubricants, engine fuels, compressor oils, lubricating greases, and so forth. The lubricating oil compositions of this invention can be made by adding the molybdenum compositions, and any supplemental additives, to an oil of lubricating viscosity. The method or order of component addition is not critical. Alternatively, the molybdenum compositions, along with any additional additives, can be added to the oil as a concentrate.